GDD 's or GDU's does anybody use them

No I am not talking swear words, although I have used many of those as well. I am talking Growing Degree Days or Growing Degree Units. Does anyone use them in planning their hay management? I am interested to hear what others have to say. Useful? Not? How do you use them if you do? Feel free to chime in.



Thanks

Forrest



GDD 's or GDU's does anybody use them